Climate change, air pollution and maternal and newborn health: An overview of reviews of health outcomes

Background Climate change represents a fundamental threat to human health, with pregnant women and newborns being more susceptible than other populations. In this review, we aimed to describe the current landscape of available epidemiological evidence on key climate risks on maternal and newborn health (MNH). Methods We sought to identify published systematic and scoping reviews investigating the impact of different climate hazards and air pollution on MNH outcomes. With this in mind, we developed a systematic search strategy based on the concepts of ‘climate/air pollution hazards, ‘maternal health,’ and ‘newborn health,’ with restrictions to reviews published between 1 January 2010 and 6 February 2023, but without geographical or language restriction. Following full text screening and data extraction, we synthesised the results using narrative synthesis. Results We found 79 reviews investigating the effects of climate hazards on MNH, mainly focussing on outdoor air pollution (n = 47, 59%), heat (n = 24, 30%), and flood/storm disasters (n = 7, 9%). Most were published after 2015 (n = 60, 76%). These reviews had consistent findings regarding the positive association of exposure to heat and to air pollution with adverse birth outcomes, particularly preterm birth. We found limited evidence for impacts of climate-related food and water security on MNH and did not identify any reviews on climate-sensitive infectious diseases and MNH. Conclusions Climate change could undermine recent improvements in maternal and newborn health. Our review provides an overview of key climate risks to MNH. It could therefore be useful to the MNH community to better understand the MNH needs for each climate hazard and to strengthen discussions on evidence and research gaps and potential actions. Despite the lack of comprehensive evidence for some climate hazards and for many maternal, perinatal, and newborn outcomes, we observed repeated findings of the impact of heat and air pollutants on birth outcomes, particularly preterm birth. It is time for policy dialogue to follow to specifically design climate policy and actions to protect the needs of MNH.

-Seasonal patterns may increase the risk of preterm birth (5/8 studies found increased incidence of preterm births during the summer).
-Seasonal patterns may increase the risk of stillbirths (3 /4 studies found increased incidence of stillbirth during the winter).
-Seasonal patterns may influence birth weight (lowest mean birth weights observed in summer and winter in 5/10 studies).
-Exposure to high ambient temperatures during pregnancy is associated with preterm births (4/6 studies).
-Inconsistent evidence with regards to ambient temperature exposure during pregnancy and birth weight.
Risk of bias: no evidence of quality assessment.

TePoel MRW (2011).
To systematically review the evidence on the relationship between seasonality and risk of -Seasonality.
-Hypertensive disorders of pregnancy= 20 studies (14 conducted in non-tropical settings, 6 conducted in tropical settings) 20 studies included in the systematic review.
-Seasonal patterns in non-tropical settings may increase the rate of hypertensive disorders of pregnancy (highest rates of hypertensive disorders of pregnancy observed during the winter in 11/14 studies).
Risk of bias: no evidence of quality assessment.

Review aim Climate Hazards* MNH Outcomes** Number of included studies & Key Findings Other Information
pre-eclampsia and eclampsia through a narrative review approach.
-Seasonal patterns in tropical settings may increase the rate of hypertensive disorders of pregnancy (highest rates of hypertensive disorders of pregnancy observed during the wet and rainy season in 5/6 studies).
To systematically assess the association between temperature and child (0-18 years) mortality and morbidity through a narrative review approach.
-Exposure to high temperatures is associated with increased risk of child mortality (9/10 studies), particularly in children under one year of age (4/10 studies).
To systematically examine the evidence of an association between high environmental temperatures and preterm birth through a narrative review approach.
-PTB=7 studies 7 papers included in the systematic review.
-Exposure to high ambient temperature during pregnancy is associated with preterm births (5/7 studies).
Risk of bias: Quality assessment conducted for all included studies.
Xu Z (2014).To systematically assess the association between -Temperature (heat waves) -Child mortality=9 studies -Child morbidity= 5 studies 12 studies included in the systematic review.
-Inconsistent evidence with regards to exposure to heat waves and increased risk of child mortality.
Risk of bias: no evidence of quality assessment.-Exposure to heat waves is associated with increased risk of child hospital admissions (2/5 studies)
To synthesize evidence on the effects of meteorology on pregnancy outcomes through a narrative review approach; to conduct a meta-analysis and present meta-effect size estimates. -Seasonality.
90 studies were included in the systematic review.
-A meta-analysis including 530,160 births (7 studies) showed an increased risk of preeclampsia for women with conception during the hottest months of the year (pooled relative risk (RR)=1.25,95% CI (1.10, 1.42) for August).
-Exposure to high temperature during the month or in the days preceding birth is associated with decreased gestational length.A meta-analysis of 63,227,292 births (6 studies) showed peaks of preterm birth at the beginning of summer (pooled relative risk (RR)= 1.19, 95% CI (1.14, 1.23).
-Birth weights are lower for births occurring in winter and summer.A meta-analysis of 70,625,872 term and preterm births (6 studies) showed lowest birth weights in the months of December and July.Similar findings derived from a meta-analysis of 5,398,360 term births.
Systematic review and meta-analysis.
Risk of bias: no evidence of quality assessment.
-Hypertensive disorders of pregnancy (gestational hypertension, pre-15 studies were included in the systematic review. Risk of bias: no evidence of quality assessment.eclampsia, eclampsia) =7 studies.
Note: no definitions provided for MNH outcomes.
-Exposure to high temperatures or low temperatures during pregnancy is associated with increased risk of preterm birth in 3/5 studies.
-Inconsistent evidence of association between season of delivery or conception and risk of developing pre-eclampsia.

Megaw L (2017).
To systematically review the literature on the relationship between ultraviolet (UV) radiation and singleton pregnancy outcomes through a narrative review approach.
-Hypertensive disorders of pregnancy = 2 studies -Birth weight = 3 studies -Gestational length (including PTB) = 2 studies 7 studies included in the systematic review.
-Inconsistent evidence with regards to the effect of UV radiation exposure on fetal growth.
-Increases in the annual average UV index associated with increased preterm birth (1 study, p<0.0001).
-Inconsistent evidence with regards to UV radiation exposure during pregnancy and development of hypertensive disorders of pregnancy.
Risk of bias: Quality assessment conducted for all included studies.

Kuehn L (2017).
To assess how extreme heat affects maternal, fetal and neonatal health., through a -Temperature (heat and heat waves).
-High temperature exposure during pregnancy is associated with increased risk of preterm birth in 15/17 studies and increased risk of early term birth in 5/6 studies.
Risk of bias: no evidence of quality assessment.-High temperature exposure during pregnancy is associated with increased risk of low birth weight in 3/5 studies.

Review aim
-High temperature exposure during pregnancy is associated with increased risk of stillbirth in 2/3 studies.
-Evidence of effect modification within infant death rates during warm seasons (1 study).

Zhang Y (2017).
To review epidemiologic al evidence on the relationship between temperature exposure during pregnancy and PTB, LBW and stillbirth through a narrative review approach. .
. 36 studies included in the systematic review.
-High temperature exposure during pregnancy is associated to decreased gestational length across different climate zones in 21/24 studies.
-High temperature exposure during pregnancy is associated to reduced birthweight in 12/14 studies.
-High temperature exposure during pregnancy is associated with increased risk of stillbirth in 4/4 studies.
Risk of bias: Quality assessment conducted for all included studies.

Ravanelli N (2018).
To determine the critical environmental and exposure limits for exercise and/or heat -Temperature (heat). -Humidity.
- -High temperature exposure during pregnancy is associated to increased risk of stillbirths (8/8 studies).In a meta-analysis of 3 studies, the odds of stillbirth per 1°C temperature increase increased by 1.05-fold 95%CI (1.01,1.08)and in a meta-analysis of 3 studies the odds of stillbirth during exposure to high temperatures over a trimester or all of pregnancy were 3.39-fold higher 95%CI (2.33,4.96).
Preston EV (2020).-Higher incidence/prevalence of GD diagnosis during the summer and lower incidence during the winter (7/12 studies).
-Inconsistent evidence with regards to the association between blood glucose levels during pregnancy and seasonality.
-High temperature exposure on the day of the GD screening or in the days/weeks prior to the GD screening is associated with increased risk of GD diagnosis (5/8 studies) and increased blood glucose levels (7/ 8 studies).
Risk of bias: Quality assessment conducted for all included studies.-Exposure to high temperatures during pregnancy is associated with preterm births (2/3 studies).

Review aim
-Exposure to high ambient temperature during pregnancy is associated with reduced birth weight (1 study).
Risk of bias: no evidence of quality assessment.-Temperature (heat/cold).

Review aim
-Stillbirth=12 studies 12 studies included in the systematic review.
-High temperature exposure during pregnancy is associated to increased risk of stillbirth (12/12 studies).
Risk of bias: Quality assessment conducted for all included studies.
To assess the association between environmental heat exposure during pregnancy and congenital anomalies through a narrative review approach.
13 studies included in the systematic review.
-High temperature exposure during pregnancy is associated with increased risk of cardiac anomalies in 3/6 studies.
-Inconsistent evidence of association between high temperature exposure during pregnancy and neural tube defects and orofacial cleft/ cranial defects.
-High temperature exposure during pregnancy is associated with decreased risk of hypothyroidism in 2/2 studies.
Risk of bias: no evidence of quality assessment.

Khoshhali M (2021).
To systematically assess whether seasonal variations and temperature is associated with increased -Seasonality -Temperature (heat) -GD= 13 studies 13 studies included in the systematic review.11 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.84 studies included in the systematic review.

Review aim
-High temperature exposure during pregnancy is associated with preterm birth (40/44 studies).
-High temperature exposure during pregnancy is associated with low birth weight (16/21 studies).
-High temperature exposure during pregnancy (mostly first trimester exposure) is associated with increased risk of congenital cardiac anomalies (5/11 studies).
-High temperature exposure during pregnancy is associated with increased risk of stillbirth (10/10 studies).
Risk of bias: no evidence of quality assessment.
-High temperature exposure during pregnancy is associated with low birth weight (5/11 studies).
-High temperature exposure during pregnancy is associated with increased risk of stillbirth (9/9 studies).
-High temperature exposure during pregnancy is associated with increased risk of gestational diabetes diagnosis, higher glucose levels and increased prevalence of gestational diabetes (8/8 studies).
Risk of bias: no evidence of quality assessment.-Inconsistent evidence with regards to the association between high temperatures and neonatal mortality and morbidity.

Review aim
-Inconsistent evidence with regards to the association between high temperatures and small-for-gestational age.
-Inconsistent evidence with regards to the association between high temperatures and congenital anomalies.
-Inconsistent evidence with regards to the association between high temperatures and miscarriage.

Edney JM (2022).
To systematically investigate how hot weather conditions may affect hydration levels in exclusively breastfed infants and impact infant feeding practices in low-and--Temperature (heat). -Humidity.
-Effects on hydration levels in exclusively breastfed infants= 9 studies -Effects on feeding practices= 9 studies Note: there is no formal measurement methodology for dehydration in infants-a mix of measures has been used to assess dehydration including urine specific gravity (USG), urine osmolality (UO), urine 18 studies included in the systematic review.
-Exclusively breastfed infants under hot conditions maintain normal hydration levels without concentrating urine to maximal levels (9/9 studies).
-Exclusively breastfed infants can maintain normal hydration levels in hot and humid conditions (4/9 studies).
-Feeding practices may be affected by temperatures through various pathways (including beliefs that infants require supplementary liquids or increased seasonal demands on woman's time).
Risk of bias: Quality assessment conducted for all included studies.-Exposure to high temperatures is associated with increased infant mortality (6/6 studies).

Review aim
-Inconsistent evidence with regards to temperature and sudden infant death syndrome.
-Exposure to high temperatures is associated with increased hospital visits or admissions for all cause morbidity in infants and for heat related morbidity in newborns (4/4 studies).
-Exposure to high temperatures is associated with increased risk of higher INR (1 study) and of being referred for neonatal jaundice (1 study).
Risk of bias: Quality assessment conducted for all included studies.
To systematically assess the association between seasonal variation and postpartum depression; to perform a meta-analysis.
-Seasonality -Postpartum depression (PPD)= 5 studies 5 studies included in the systematic review.5 studies included in the meta-analysis.
-Season of delivery is associated with the risk of PPD, as women giving birth in spring, summer of autumn have a lower risk of PPD compared to those that give birth in winter (RR: 0.83, 95%CI (0.78-0.88)).
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Aberese-Ako M (2022).
To present the findings on the factors that motivate or demotivate Temperature (heat) Motivators to access malaria health services in pregnancy 24 studies included in the meta-ethnographic review.
Risk of bias: no evidence of quality assessment.-Warm weather demotivates pregnant women from using long-lasting insecticidal nets (5/24 studies).

Review aim
-Warm weather, coupled with long distances, demotivates pregnant women from accessing antenatal care health services (3/24 studies).
* Timing of exposure varies; method of measurement of the exposure varies.
**The provided definitions of MNH outcomes are aligned with established definitions in the literature, unless otherwise specified.
Table S4b.Reviews on air pollution and MNH outcomes (N=47).

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
Bonzini M (2010).
To systematically synthesize the evidence on the association between maternal exposure to ambient air pollution and birth outcomes through a narrative review approach.
-Exposure to PM10 during pregnancy is associated with increased risk of preterm birth (6/8 studies).
-Exposure to PM10 during pregnancy is associated with increased risk of low birth weight at term (2/7 studies).
Risk of bias: no evidence of quality assessment.

Bosetti C (2010).
To systematically synthesize the evidence on the association between maternal exposure to ambient air pollution and pregnancy outcomes through a narrative review approach.
-Exposure to particulate matter during pregnancy is associated with increased risk of preterm birth (8/13 studies).
-Exposure to particulate matter during pregnancy is associated with increased risk of low birth weight (11/17 studies).
-Exposure to particulate matter during pregnancy is associated with increased risk of small for gestational age (2/4 studies).
Risk of bias: no evidence of quality assessment.

Veras MM (2010).
To systematically assess the evidence on the association between exposure to air pollution and reproductive, fetal and neonatal health outcomes through a narrative review approach and with a particular focus on Brazil.
-Prenatal exposure to ambient air pollution is associated with increased risk of preterm birth (6/7 studies).
-Prenatal exposure to ambient air pollution is associated with increased risk of low birth weight (9/10 studies).
-Prenatal exposure to ambient air pollution is associated with increased risk of preterm birth (5/7 studies) or reduced duration of gestation (2/7 studies).
Risk of bias: no evidence of quality assessment.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
-Exposure to ambient air pollution is associated with increased risk of neonatal deaths (2/3 studies) and infant mortality (2/6 studies).Shah PS (2011).
To systematically review the literature on the impact of air pollution on birth outcomes among pregnancies of women exposed to various pollutants and summarize the findings through a narrative review approach.
-Inconsistent evidence with regards to the association between air pollution and preterm birth.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
Pedersen M (2014).
To systematically review epidemiological studies investigating associations between air pollution and hypertensive disorders of pregnancy and to perform a metaanalysis.
-NO -NO2 -CO -O3 -Particulate matter (PM 2.5 and PM 10) -Hypertensive disorders of pregnancy= 17 studies 17 studies included in the systematic review.16 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.
To systematically synthesize the evidence on the association between exposure to ambient air pollution during pregnancy and congenital anomalies, and to perform a meta-analysis.
Systematic review and meta-analysis.
Risk of bias: no evidence of quality assessment.

Frutos V (2015).
To systematically synthesize the evidence on the effects of exposure to ambient air pollution on fertility outcomes in humans and mammals through a narrative review approach.
-Exposure to air pollution is associated with a detrimental effect on live birth rate (3/3 studies).
-Exposure to air pollution is associated with an increased risk of miscarriage (3/4 studies).
Risk of bias: Quality assessment conducted for all included studies.
To systematically synthesize the evidence on the -NO2 -CO -O3 -Exposure to air pollution is associated with a detrimental effect on live birth rate (2/3 studies).
-Exposure to air pollution is associated with a detrimental effect on implantation rates (2/3 studies).
-Exposure to air pollution is associated with an increased risk of miscarriage in the general population (2 studies) and in women undergoing fertility treatments (1 study).Siddika N (2016).
To systematically assess the evidence on the association between prenatal exposure to air pollution and stillbirth and to perform a metaanalysis.
-Particulate matter (PM 2.5 and PM 10) -NO2 -CO -SO2 -Stillbirth=13 studies 13 studies included in the systematic review and in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies Hehua Z (2017).
To systematically synthesize the evidence on the association between prenatal exposure to ambient air pollution during pregnancy and incidence or prevalence of asthma from birth up to 14 years of age providing risk estimates.
Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
Li X (2017).
To systematically assess the evidence on the association between prenatal exposure to air pollution (fine particulate matter) and pregnancy and/or birth outcomes, and to perform a metaanalysis.
-Particulate matter (PM 2.5) -LBW= 15 studies -PTB=14 studies 23 studies included in the systematic review and in the meta-analysis.
-The pooled OR for the association between PM2.5 exposure, per interquartile range increment, and term low birth weight throughout pregnancy was 1.03 (95% CI: 1.02,1.03).
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Melody SM (2018).
To synthesize the existing literature on the relationship between maternal exposure to acute short term to medium term changes in outdoor air quality (such as wildfires) and obstetric and neonatal outcomes through a narrative review approach.
-Short to medium term periods of poor air quality.
-Inconsistent evidence with regards to exposure to acute changes in air quality (air pollution exacerbation events) during pregnancy and birth weight/low birth weight.
-Exposure to acute changes in air quality during pregnancy is associated with increased risk of preterm birth (3/3 studies).
Risk of bias: Quality assessment conducted for all included studies.
To systematically assess the evidence on the association between prenatal -Particulate matter (PM 10) -NO2 -SO2 Congenital heart disease=4 studies 69 studies included in the systematic review of which 4 studies focusing on ambient air pollution.
Risk of bias: no evidence of quality assessment.-Prenatal exposure to NO2 is associated with increased risk of congenital heart disease (2/4 studies).

Review aim
-Prenatal exposure to SO2 is associated with increased risk of congenital heart disease (1/4 studies).
-Prenatal exposure to PM10 is associated with increased risk of congenital heart disease, particularly atrial septal defects and patent ductus arteriosus (2/4 studies).Klepac P (2018).
To systematically assess the evidence on the association between prenatal exposure to ambient air pollution and pregnancy outcomes, and to perform a meta-analysis.

*number of studies per outcome unclear
96 studies included in the systematic review and 28 studies included in the meta-analysis.
-Exposure to particulate matter (PM 10-PM 2.5) is associated with increased risk of preterm birth (2/2 studies).
-Inconsistent evidence with regards to exposure to drinking water contaminants and preterm birth.
-Inconsistent evidence with regards to exposure to organic compounds and preterm birth.
Risk of bias: no evidence of quality assessment.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
-Exposure to tobacco smoke during pregnancy is associated with increased risk of preterm birth as well as fetal growth restriction (20/20 studies).
-Exposure to toxic metals during pregnancy is associated with increased risk of preterm birth (2/2 studies).
Bekkar B (2020).-Exposure to air pollutants during pregnancy is associated with increased risk of low birth weight (25/29 studies; 18.5 million total births; increased risk median 10.8% range (2.0-3.6) for whole pregnancy PM 2.5 exposure).
Risk of bias: no evidence of quality assessment.

Zhang H (2020).
To systematically review the literature on the effect of exposure to air pollution on the risk of gestational diabetes and to perform a metaanalysis.
-No significant association was found in the first or second trimester exposure to O3. Pre-pregnancy exposure to O3 is inversely associated with GDM risk (standardized OR = 0.981, 95% CI: 0.977, 0.985).
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
-No significant association was observed in prepregnancy, first trimester or second trimester exposure to PM2.5 or PM10 or NO2.

Bai W (2020).
To systematically investigate the effect of trimester-specific exposure to air pollution on hypertensive disorders of pregnancy and gestational diabetes and to perform a meta-analysis.
-Exposure during the first trimester to SO2 is significantly associated with increased risk of GD (RR = 1.04, 95% CI: 1.00-1.08 per 1 parts per billion increment).
Systematic review and meta-analysis.Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
Simoncic V (2020).
To systematically investigate the literature on the relationship between air pollution and adverse birth outcomes in Europe and to perform a meta-analysis.
-The findings of the systematic review do not show statistically significant results, although a trend is apparent in that NO2 exposure during the whole pregnancy seems to increase the prevalence of LBW.
-The findings of the meta-analysis do not reveal statistically significant results.
Systematic review and meta-analysis.
Risk of bias: no evidence of quality assessment.
To systematically investigate the association between air pollution and head size at birth through a narrative review approach.
-PAH (polycyclic aromatic hydrocarbons) -NO2 -NO -CO -Particulate matter (PM 2.5 and PM 10) -Impact on head size at birth 13 studies included in the systematic review.
-Inconsistent evidence on the relationship between prenatal exposure to air pollution and head size at birth.
Observational study and systematic review.Risk of bias: no evidence of quality assessment.

Padula AM (2020).
To systematically assess the evidence on the association between prenatal exposure to air pollution and heavy metals and infant and child health outcomes through a narrative review approach.
-The prenatal exposure to air pollutants is associated with LBW (3/4 studies) and PTB (3/3 studies), while the evidence for SGA is inconclusive.
-When combining the effects of air pollution and socioeconomic status on birth outcomes, the associations appear to be stronger.
Risk of bias: no evidence of quality assessment.
To systematically assess the evidence on the association between exposure to air pollution and -Particulate matter (PM 2.5 and PM 10) -NO2 -NOx -GD= 13 studies 13 studies included in the systematic review and in the meta-analysis.
-The meta-analysis showed that exposure to PM2.5 was not associated with the increased risk of GDM (adjusted Systematic review and meta-analysis.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
gestational diabetes and to perform a meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Steinle S (2020).
To assess the evidence on the association between prenatal exposure to particulate matter and birth weight or changes in birth weight, through a narrative review approach.
-Particulate matter (PM 2.5 and PM 10) -LBW=9 studies -Changes in birth weight= 4 studies 13 studies included in the systematic review.
-Exposure to particulate matter pollution during pregnancy is associated with low birth weight, with most meta-studies finding statistically significant point estimates (6/9 studies).
-Exposure to particulate matter pollution during pregnancy is associated with reductions in birth weight (4/4 studies).
Risk of bias: no evidence of quality assessment.

Zhang H (2021).
To perform a systematic review and meta-analysis of the association between air pollution and stillbirth.
-Exposure to CO during the third trimester and exposure to O3 during the first trimester also increased the odds of stillbirth, with the standardized ORs and 95% CIs of 1.0009 (1.0001-1.0017)and 1.028 (1.001-1.055),respectively.
Systematic review and meta-analysis.Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
-First trimester O3 exposure was significantly associated with stillbirth, with the standardized OR and 95% CI were 1.002 and 1.001-1.004,respectively.

Aghababaeian H (2021).
To systematically investigate the literature on the impacts of dust storms on human health through a narrative review approach.
-Particulate matter (PM 2.5 and PM 10) -PTB=1 study -Birth weight (including LBW) = 2 studies 140 studies included in the systematic review.3 studies provided estimates for MNH outcomes.
-Exposure to dust storms during pregnancy is associated to increased risk of preterm birth (1 study) and to increased risk of LBW (1 study).
Risk of bias: Quality assessment conducted for all included studies.

Amjad S (2021).
To systematically summarize the evidence on the association between maternal exposure to wildfires and adverse pregnancy outcomes through a narrative review approach.
-Exposure to wildfire smoke during pregnancy is associated with a reduction in mean birth weight (range -4.8 grams per 1 μg/m3 increase in gestational average daily smoke exposure to 18.0 grams for overall exposure) (6/7 studies).
-Inconsistent evidence with regards to the association between wildfire smoke exposure and SGA.
-Inconsistent evidence with regards to the association between wildfire smoke exposure and PTB.
Risk of bias: Quality assessment conducted for all included studies.

Henry S (2021).
To systematically synthesize the evidence on the risk of respiratory related healthcare visits among children aged 0-18 years following exposure to wildfire smoke.
16 studies included in the systematic review.
-Exposure to wildfire smoke is associated to increased respiratory visits to the emergency department (8/16 studies).
Risk of bias: Quality assessment conducted for all included studies.

Cao L (2021).
To systematically synthesize the evidence on the -Particulate matter (PM 2.5 and PM 10) -Hypertensive disorders of pregnancy (gestational 17 studies included in the systematic review and metaanalysis.
Systematic review and meta-analysis.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
association between maternal exposure to particulate matter and hypertensive disorders of, and to perform a metaanalysis.
Risk of bias: Quality assessment conducted for all included studies.

Ma Z (2021).
To systematically synthesize the evidence on the association between prenatal exposure to ambient air pollution and congenital heart diseases, and to perform a metaanalysis.
-Particulate matter (PM 2.5 and PM 10) -NO2 -SO2 -CO -O3 -Congenital heart disease= 24 studies 24 studies included in the systematic review and in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Uwak I (2021).
To systematically synthesize the evidence on the association between prenatal exposure to particulate matter air pollution and birth weight, and to perform a metaanalysis.
-Particulate matter (PM 2.5 and PM 10) -Birth weight=53 studies 18 studies included in the systematic review and 33 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Isaevska E (2021).
To systematically assess the evidence on the association -Particulate matter (PM 2.5 and PM 10) -DNA methylation status in cord blood/placenta=30 studies 32 studies included in the systematic review.Risk of bias: no evidence of quality assessment.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
between exposure to air pollutants during the first 1000 days of life (from conception to 2 years) and changes in DNA methylation pattern in cord or newborn blood and/or in children through a narrative review approach.
-NO2 -SO2 -CO -O3 -DNA methylation studies in childhood= 5 studies -Exposure to ambient air pollution exposure during pregnancy (particularly in the first trimester) is associated with global loss of methylation in newborn cord blood and placenta, indicating the beginning of the pregnancy as a potential period of susceptibility.
To systematically assess the evidence on the association between prenatal exposure to air pollution (fine particulate matter) and stillbirth and to perform a metaanalysis.
-Particulate matter (PM 2.5) -Stillbirth=7 studies 7 studies included in the systematic review and 6 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Yu G (2021).
To systematically assess the evidence on the association between prenatal exposure to air pollution (particulate matter) and congenital anomalies, and to perform a meta-analysis.
-Particulate matter (PM 2.5 and PM 10) -Congenital anomalies= 30 studies 30 studies included in the systematic review and metaanalysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies Ravindra K (2021).
To systematically assess the evidence on the association between prenatal -Particulate matter (PM 2.5 and PM 10) -NO2 -Congenital anomalies= 26 studies 26 studies included in the systematic review and in the meta-analysis.
-The meta-analysis showed that prenatal exposure to air pollution is associated with increased risk of Systematic review and meta-analysis.-Inconclusive results with regards to the association between prenatal exposure to air pollution and cognitive abilities, development of attention deficit and hyperactivity disorder, mood disorders and brain abnormalities.

Review aim
Risk of bias: no evidence of quality assessment.

Ghosh R (2021).
To systematically assess the evidence on the association between exposure to air pollution particulate matter and perinatal outcomes, and to perform a metaregression.
-Particulate matter (PM 2.5 ) -Birth weight=44 studies -LBW= 40 studies -PTB= 40 studies 124 studies included in the systematic review and in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies Markozannes G (2022).
To perform an umbrella review to evaluate the strength of the association between exposure to ambient air pollution -Particulate matter (PM 2.5 and PM 10) -NO2 -SO2 -CO -O3 -Hypertensive disorders of pregnancy (gestational hypertension, pre-eclampsia) =1 study -SGA=3 studies -LBW=3 studies 75 studies included in the umbrella review; 4 studies focused on MNH outcomes.
-10 μg/m increase of PM2.5 levels was associated with an increased risk of having an infant born small for the gestational age, (long-term exposure-entire pregnancy: Umbrella review.
Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
and adverse health outcomes.
-During the entire pregnancy, an increased risk for low birth weight was associated with a 5-ppb increase of SO2 levels (24 h average; OR: 1.035, 95% CI: 1.021 to 1.049), whereas a 10 μg/m increase of PM2.5 levels during the third trimester (long-term exposure) was associated with an increased risk for hypertension in pregnancy (OR: 2.177, 95% CI, 1.710 to 2.773).Lin LZ (2022).
To systematically synthesize the evidence on the association between prenatal exposure to particulate matter, as well as exposure during the first and second year after birth and development of autism spectrum disorders, and to perform a metaanalysis.
-Particulate matter (PM 2.5 and PM 10) -Autism spectrum disorders= 31 studies 31 studies included in the systematic review; 20 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Gong C (2022).
To systematically synthesize the evidence on the effects of prenatal exposure to particulate matter on changes in grams of term birth weight, and to perform a meta-analysis.
-Particulate matter (PM 2.5 ) -Changes in grams of birth weight at term =62 studies 62 studies included in the systematic review and 31 studies included in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies.

Review aim Air pollutants MNH Outcomes** Number of included studies & Key Findings Other Information
Nyadanu DN (2022).
To perform an umbrella review to evaluate the strength of the association between exposure to ambient air pollution and adverse birth outcomes.
-The prenatal exposure to PM2.5 showed more consistent positive associations to the outcomes of interest compared to other pollutants.
-For whole pregnancy exposure, a more consistent positive association was found for PM2.5 and birth weight reductions, particulate matter and miscarriage, and SO2 and LBW.
-Other exposure-outcome associations mostly showed less consistent positive associations and few unclear directions of associations.Almost all associations showed probable evidence.
Umbrella review.
Risk of bias: Quality assessment conducted for all included studies.
To systematically assess the evidence on the association between exposure to ambient air pollution (particulate matter) and miscarriage, and to perform a metaanalysis.
-Particulate matter (PM 2.5 and PM 10) -Miscarriage=6 studies 6 studies included in the systematic review and in the meta-analysis.
Systematic review and meta-analysis.
Risk of bias: Quality assessment conducted for all included studies Yue D (2022).
To systematically assess the evidence on the association between prenatal exposure to air pollution and development of childhood eczema, -Particulate matter (PM 2.5 and PM 10) -NO2 -SO2 -Childhood eczema= 12 studies 12 studies included in the systematic review and in the meta-analysis.
-The meta-analysis showed that prenatal exposure to NO2 (per 10 μg/m3 increased) is significantly associated to development of childhood eczema, with a pooled risk estimate of 1.13 (95% CI: 1.06-1.19),but no association was observed between exposure to PM10, PM2.5, and SO2 and the risk of eczema in offspring.
Systematic review and meta-analysis.-Prenatal exposure to CO, NO and SO2 is associated with increased risk of congenital heart disease (2 studies).
-Prenatal exposure to PM2.5 is associated with increased risk of congenital heart disease (1 study).
Risk of bias: no evidence of quality assessment.
To systematically assess the evidence on the association between prenatal exposure to particulate matter and preterm birth, and to perform a meta-analysis.
-Particulate matter (PM 2.5 and PM 10) -PTB= 84 studies 84 studies included in the systematic review and in the meta-analysis.
-Exposure to wildfires did not negatively impacts access to health care services (4/4 studies) although in one study the quality of counselling on the fires received was not considered adequate.
-Exposure to wildfires during pregnancy is associated with symptoms of post-traumatic stress disorders, and feelings of trauma and despair (3/3 studies).
-Exposure to wildfires postpartum is associated with reduced access to lactation support and lack of safe and private places, with declining breastfeeding rates during and after evacuation (1 study).Blanc N (2023).
To systematically synthesize the evidence on the effects of preconception ambient air pollution exposure on children's health outcomes, and to perform a metaanalysis.
-Preconception exposure to PM 2.5 , PM 10 , O3 and SO2 is associated to increased risk of preterm birth, low birth weight and diagnosis of autism spectrum disorder.
-Unclear evidence with regards to the association between perinatal mortality and preconception exposure to air pollution.
Systematic reviews and meta-analysis.45 studies included in the systematic review, of which 7 focusing on hurricanes and 3 on floods.
-Exposure to hurricanes during pregnancy is not associated with increased risk of preterm birth (2/2 studies); inconclusive results with regards to the association between exposure to hurricanes during pregnancy and reduction in birth weight; inconclusive results with regards to the association between exposure to hurricanes and congenital anomalies; exposure to hurricanes during pregnancy is associated with increased risk of PTSD among mothers (3 studies) that increased with increased exposure to the event.
-Inconclusive results with regards to the association between exposure to floods during pregnancy and preterm births; exposure to floods during pregnancy is associated with increased risk of reduction of birth weight (2/2 studies); inconclusive results with regards to the association between exposure to floods and SGA; exposure to floods during pregnancy is not associated with increased risk of congenital anomalies; exposure to floods during pregnancy is associated with increased risk of miscarriage (2/2 studies).
Risk of bias: no evidence of quality assessment.

Zotti ME (2013).
To systematically assess the literature on USdisaster related reproductive health outcomes through a narrative review approach.
-Hurricanes -Floods -Fetal distress= 1 study (with hurricane as the exposure) -PTB=4 studies (3 studies with hurricane as the exposure and 1 study with flood as the exposure) -LBW=4 studies (3 studies with hurricane as the exposure and 1 study with flood as the exposure) -Maternal mental health=1 study (with hurricane as the exposure) Note: no definitions provided for MNH outcomes.
15 studies included in the systematic review, of which 4 focusing on hurricanes and 1 on floods.
-Exposure to hurricanes during pregnancy is associated with an increased risk of preterm birth (2/3 studies), of a reduction in birth weight (2/3 studies) and of fetal distress (1 study) as well as of maternal mental health issues (1 study).
-Only 1 study investigated flood as the exposure during pregnancy finding an associated between the exposure and increased risk of preterm birth and of a reduction in birth weight.
Risk of bias: no evidence of quality assessment.

Review aim Disaster type MNH Outcomes** Number of included studies & Key Findings Other Information
Saulnier DD (2015).
To systematically assess the literature on the health effects of prenatal exposure to disasters through a narrative review approach.
-Hurricanes -Floods -Short-and long-term health effects following prenatal exposure to disasters 47 studies included in the systematic review, of which 3 focusing on hurricanes and 1 on floods.
-Prenatal exposure to hurricanes is associated with increased risk of fetal distress (1 study), of autism (1 study), and of diabetes and hypertension later in life (1 study).
-Only 1 study investigated prenatal exposure to floods in relation to schizophrenia finding no evidence of an association.
Risk of bias: no evidence of quality assessment.

Mallet LH (2018).
To systematically present the findings on flood related risks during pregnancy and childhood through a narrative review approach.
141 studies included in the systematic review.
-Exposure to flooding during pregnancy is associated with increased risk of mortality among pregnant women (2 studies).
-Exposure to flood is associated with increased risk of perinatal mortality (2 studies).
-Exposure to flooding is associated with increased risk of under 5 mortality (2 studies).
-Exposure to floods during pregnancy is associated with increased risk of fetal distress (1 study).
-Exposure to floods during pregnancy is associated with increased risk of low birth weight (3 studies).
-Exposure to floods during pregnancy is associated with increased risk of miscarriage (2 studies).
-Exposure to floods is associated with increased risk of mental health conditions, including PTSD among pregnant women (4 studies).
Risk of bias: no evidence of quality assessment.
To perform a meta-analysis to estimate the magnitude of the effects of disaster -Floods -Effects of prenatal maternal stress on the offspring (birth outcomes, cognitive development, motor outcomes, physical outcomes, socioemotional outcomes) 30 studies included in the systematic review and in the meta-analysis, of which 20 focusing on floods.
-The meta-regression observed a significantly positive overall association between prenatal maternal stress Systematic review and meta-analysis.and offspring motor outcomes in flood related effect sizes (r = 0.0741; SE= 0.0153; p>0.0001) and a significantly positive overall association between prenatal maternal stress and offspring behavioural outcomes in flood related effect sizes (r = 0.0752; SE= 0.0170; p>0.0001).

Review aim
conducted for all included studies.
To systematically present the findings of the literature on key issues related to infant feeding in emergencies in middle-or highincome countries.
-Hydrometeorological and geophysical disasters -Effects on infant feeding 30 studies included in the scoping review, of which 15 focusing on hydrometeorological and/or geophysical disasters.
-The most common challenges for breastfeeding mothers in the context of disasters include lack of privacy or of adequate environment to breastfeed (11 studies), stress/exhaustion (12 studies), limited fluid/nutritious intake for mothers (8 studies), lack of time (4 studies).Additionally challenges include lack of breastmilk expression equipment (1 study) and no electricity for breastmilk storage (1 study).
Risk of bias: no evidence of quality assessment.

Rodriguez-Soto (2021).
To systematically present the findings on the association between prenatal maternal stress during pregnancy and childhood temperament through a narrative review approach.
-Hurricanes -Floods -Windstorms -Child temperament 20 studies included in the systematic review, of which 3 focused on windstorms, 2 on floods and 1 on hurricane.
-Exposure to windstorms during pregnancy is associated with increased risk of negative affectivity in the offspring (3/3 studies. -Exposure to floods during pregnancy is associated with increased risk of greater toddler reactivity (2 studies).
-Exposure to hurricanes and flooding during pregnancy is associated with increased risk of difficult temperament at 12 months (1 study).-Water salinity (drinking water) -Hypertensive disorders of pregnancy= 3 studies 10 studies included in the systematic review.3 studies focused on a pregnant population: the findings of these three studies are reported descriptively given the small number.
-Inconsistent evidence with regards to the association between drinking water salinity and development of hypertensive disorders of pregnancy.
in the systematic review.
and newborn health.PTB: preterm birth.LBW: low birth weight.PTSD: post-traumatic stress disorder.SGA: small for gestational age.* Timing of exposure varies; method of measurement/assessment of the exposure varies.**The provided definitions of MNH outcomes are aligned with established definitions in the literature, unless otherwise specified.
and newborn health.* Timing of exposure varies; method of measurement/assessment of the exposure varies.**The provided definitions of MNH outcomes are aligned with established definitions in the literature, unless otherwise specified.

Climate Hazards* MNH Outcomes** Number of included studies & Key Findings Other Information
Timing of exposure varies; method of measurement of the exposure varies.**The provided definitions of MNH outcomes are aligned with established definitions in the literature, unless otherwise specified. *

Table S4d .
Reviews on water security, quality and availability and MNH (N=1).
* Timing of exposure varies; method of measurement/assessment of the exposure varies.**The provided definitions of MNH outcomes are aligned with established definitions in the literature, unless otherwise specified.